Dental impression composition comprising a copolymer of vinyl chlorhoe and vinyl acetate, di-normal propyl phthalate and a filler



Patented June 10, 1952 UNIERE-Di PAT-sur orrrcs DENTAL LIMBJR-IESSI ON COMRG SITIONnCOMi-s;

PRISING A 'COPQLYMERiDE TVINYL' ICHLCQJEi Frank J. Sowa,Cranford, and-Max- M% S clrwartz Jersey City, N:"J.;' said Sowa-assignor tosaith.

Schwartz.

N o..Drawingb. Application November 4,.;1 9,48,- SeriaLNO. 58,354 1 3 Claims; (Ci. 2601-1 23118) Our invention relates to oompositionsior-=use in taking dental impressionsand is directed par-' ticularly' to compositions --Which V are characterizedby the dimensional stability of the finished impression.

Dentalimpression-oompositions developed and used heretofore have ingeneral been oftwo types;

namely; plasters,- -gumsorwaxeswhich set up orharden to- ;form- -a -rigid,'stifi or inflexible body; and- -compositions containing alginates- -o1 resins which form relatively softer'andmore fiexible im pressionsr Plasters; gumsand Waxes are unsatisfactory-because the-impressionis =irequently broken or distorted on being remevedfrom thepatients mouthparticularly Whenteeth are pres--' ent or -there-are-anyundercut or-rounded surfaces beneath whichthe =-composition extends.

Moreover when plaster breaks or crumbles,-par

ticles-of theplaster may fall into the patients throatcausing serious discomfort or injury Gums and Waxes'are furthersobjectionablebecause theymust be introducedintoi the :patients mouth ina heated .-condition andzoften must..be cooled by the use of a stream of Water or by employing a.

Water-cooled impression tray.-

Those compositions Which'produce a more fiexie; b16101 resilient impression have the advantage. of greateraccuracy and easeofremoval; How

ever they-have-always contained Water or volatile solvents which evaporate as the composition sets Attempts. havebeen madev to overcome such dimensional changes by coating the impression with oil or a sealing material but such steps are troublesome, are not always effective, andthey frequently cause the loss of detail. The, use of solvents is alsorvobjectionable because" they must. be largely evaporated .whilethe composition is.in the patients mouth. Moreover the surfaces vof the gums and mouth engaged by the composition are very sensitive and are oftentender whereas a great majority of the solvents or liquids usable. with gums and resinsproduce a severe burning sensation when brought into contact with such tissues and therefore cannot be; employed in dental impression materials.

Many of-the plastic dental impression 'com;-" poundshave other objectionableproperties: i Thus the alginates will not adhere to most surfaces-andtherefore require a special perforated impression- ."30 and after the impression is removed v from-themoutha They therefore shrinkor become; distort ed on standing with the. result that it is -neces-. sary to pour. the plaster or. stonevused/inmaking, the model promptly after the impression istaken.

trayz-- Moreovem the tray-era impression cannot bebuiltup-or extendedrvith wax orother mate rials as is -frequently desirablea- Other--im-pres-- sion-oompositionsareeften sostifii-that-they-cause distortion -=of= the surfaces the -engage,- or they are so flexibleand s'of-tthat theydo znot' support I the-p1asteror'- stone used in fo rming the-model so that distortions are -=-in treduoed z:l1. .i in=g =-the casting operations In accordance-with our inventionpthese-=objections to"compositions-of theprior art'are over a come and --mater-ialsare provided:- for producing dental impressionspossessing the-desiredresiliem cy andflxibi-lit'y but-ha-ving-the-requisite'bodyto insure the-greatest:- accuracyin lthe finishedimpression-and resulting models Atthe same-time, the 'impressions arecharaeterizedeloy substantially -permanent dimensionalivstaibilityi without r-re-' sorting to =the' -use of -sealing materiaislv orz coating compouns for -'preser-ving -the=--impression;- These advantages are preferably attained by employin'gsresinous compounds incom bination :with

a '-non volatile -plasticizer withor without a solvating agent- Which converts; the resin' into' I, a i

gel-dike bod-y underllthe conditions of use: a The resultingqimpressionis found to -retain itsdimensional stab-i li ty over long periods -of time and does ing a =-resincus substanceand a non-volatile plasticizer with or without a solvating agent;-

These "and other -obj'ects and 'features-- of the present invention-will 'appear from the ollowingdescription thereof-yin which reference is nrade to typical compositions'and-methods of procedure for--thepurpose Of'} indicating-the nature of our invention but without intending to limit ourinvention'tl'rerebyr:

In gene1 a1 dental--impre'ssion= I materials 1 embodying our invention are' produ'oed by mixing-a a dry-powdered resi-mcontain ing material -with'l-"ai liquid plasticizin agent at the time the impression is to be taken. The resin-containing material may include fillers, pigments or other dry ingredients whereas the liquid plasticizer may be mixed with other liquid constituents such as accelerators, bufling agents, flavoring substances or the like.

The prefered type of resinous material used in forming impression compositions for use in to sustain the plaster or stone used in forming a model. When the amount of vinyl chloride in the copolymer is less than 90% the composition is generally softer and more sticky whereas with higher percentages of vinyl chloride in the copolymer it is usually preferable to use an accelerator in order to cause the resin to assume the desired gel-like condition within the time permissible for taking a dental impression.

The resins described may be used in substantially pure state and in finely powdered condition. However, for greater economy, body and smoothness we prefer to employ up to 50% by weight of an inert filler in the powdered product. Typical of such fillers are zinc oxide, talc, powdered limestone or the like. It is usual also to add a pigment, such as cadmium selenide, to the mixture since the imparts the conventional pink color to the impression material. Similar- 1y, 2. flavoring agent such as oil of peppermint may be added to the dry powder or mixed with the liquid plasticizer to give the composition a pleasing taste.

The plasticizer or solvating agent employed must be chosen so as to be non-toxic and nonirritating to the surfaces engaged by the composition. Moreover, by using those plasticizers which are non-volatile, the dimensional stability of the finished impression is maintained without danger of shrinkage due to evaporation or drying out of the impression on long standing. The number of such plasticizers which may be employed is actually very limited because of the irritation and burning sensation produced by most of the esters commonly used as plasticizers and other compounds which posses plasticizing properties. We have found that the dialiphatic esters of phthalic acid, and particularly those esters in which the total carbon content of the ester group is at least 6, have the necessary plasticizing properties and yet are not irritating to the tender surfaces and tissues they engage. They also blend well with bufiing agents such as mineral and vegetable oil and other compounds that might be used as inhibitors.

Dinormal propyl phthalate is the preferred ester to employ since this compound produces substantially no irritation and is an excellent plasticizer for the vinyl chlorideacetate copolymer. However di-allyl phthalate is just as satisfactory as dinormal propyl phthalate and has the same advantages. Di-isopropyl, di-isobutyl, di n-butyl and dioctyl phthalate are also satisfactory but require an accelerator to set up into the desired final state. Similarly other plasticizing agents may be employed provided they do not produce excessive irritation, are nontoxic, and form a suitable gel. For example, various mixed esters may be employed such as allyl, n-propyl phthalate and ethyl, butyl phthalate. Mixtures of the di-aliphatic esters may be used such as mixtures containing di-allyl phthalate and di-normal propyl phthalate.

By employing accelerators in combination with the plasticizer it is possible to use resinous materials which would otherwise be unsuitable because of the slow action of the plasticizer in converting the resin into a gel-like composition. Similarly plasticizers which have little or relatively slow action on a particular resin may be employed when used in combination with a suitable accelerator. The accelerators, like the plasticizers, must be non-toxic and nonirritating to the tissues. Among the most suitable accelerators that we have used are the esters of aliphatic acids, particularly the esters of acetic acid, although ketones and chlorinated hydrocarbons, ethers and other organic compounds may be employed by themselves or in combination with the esters of aliphatic acids. One of the best accelerators we have used is butyl acetate, but we have also employed ethyl acetate, propyl acetate, isopropyl acetate, amyl acetate and isoamyl acetate. Among the ketones which may be used are diacetone alcohol, di-ethyl ketone, and methyl amyl ketone. Among the ethers which may be used are methyl, ethyl or butyl ethers of ethylene glycol. As chlorinated hydrocarbons we have used carbon tetrachloride and trichlorethylene. The amount of accelerator used varies considerably depending on the type of resin, the type of plasticizer, the type of accelerator and the degree of stiffness or body of the impression desired. Ordinarily the amount of accelerator varies from zero up to about 20% by weight of the liquid used in forming the impression composition. The amount of accelerator may be decreased or eliminated altogether if the liquid used is warmed slightly.

When using accelerators and even when using many of the plasticizers described, it is often desirable to use a diluent or buffering agent such as mineral or vegetable oils. These agents in general have a soothing effect which decreases irritation and permits the use of higher concentrations or different types of the accelerator and plasticizer. The amount of such buffering agent employed may vary from zero to 30% by weight of the liquid used in forming the impression material.

In normal dental practice, it is usually most practical to allow about one minute for the mixing of the liquid with the resin containing powder, one minute for applying the composition to the dental tray and three minutes for the composition to set up into a suitable stable condition in the patients mouth. When the composition is to set within this time limit, it is usual to employ approximately 25 equal parts by weight of the dry powder resin-containing material to from about 18 to '75 parts of the liquid material. The amount of liquid used may be varied considerably depending on the type of resin and plasticizer used and the consistency of the impression material desired. In a typical case when using 28 grams of resin powder, the amount of liquid plasticizer varies from about 18 to 75 grams.

.5 A preferred composition in which no accelerator or buffering agent is used is as follows:

21 parts by weight of a copolymer of vinyl-chloride-acetate containing 90% vinyl chloride.

7 parts by weight zinc oxide.

30 parts by weight dinormal propyl phthalate.

If desired from 1 to parts of an accelerator such as butyl acetate may be added to the plasticizer.

The dry materials consisting of the resin and the filler (with any pigment employed) are mixed together in a finely ground or pulverized form. When the impression is to be taken the liquid plasticizer and powder are mixed so as to form a smooth, relatively stiff paste. The paste does not set up at once and may be allowed to stand quite some time without setting, so that the dentist need not rush and may even stop to answer the telephone or attend to other brief duties. Thereafter, the composition may be applied to any conventional impression tray and then inserted into the patients mouth and pressed into place. As the heat of the human body raises the composition to the temperature of a patients mouth, the action of the plasticizer is apparently speeded up and the composition is converted into a somewhat stiff, gel-like, elastic body which faithfully conforms to the contours and crevices of the surfaces of the teeth and tissues engaged. Within three minutes after being applied, the impression may be removed and it is then ready to receive the plaster or stone used in forming the model. However it is not necessary to pour the model at once since it may be poured at any time, and even as long as a month or more after after the original impression was taken. Repeated castings may be made from the same impression. Partial dentures made to fit one model will fit another model made from the same impression. It is also found that partial dentures made to fit one model will fit other models made from different impressions of the same mouth. This has never been possible heretofore because of the shrinkage or distortortion resulting from evaporation of solvent or dimensional instability of the impression during the casting operation. Moreover, it is not necessary to apply oil or sealing material to the impression in order to preserve it against shrinkage. The steps required in producing and using the impression are therefore simplified whereas the greatest accuracy of the impression is assured.

Instead of using the specific composition referred to above the following composition may be used:

18 parts by weight of vinyl chloride-acetate containing 90% vinyl chloride.

parts by weight of zinc oxide.

22 parts by weight of di-butyl phthalate.

2 parts by weight of butyl acetate.

Another alternative composition for the liquid constituents is as follows:

20 parts by weight of ethyl butyl phthalate. 4 parts by weight of butyl acetate.

A further example of a liquid mixture which may be used is as follows:

20 parts by weight of diallyl phthalate. 4 parts by weight of mineral oil (Nujol).

Any of the foregoing liquid mixtures may be used with any of the copolymers of vinyl chloride-acetate containing from to 93% of vinyl chloride.

The composition may be used for taking impressions for either full or partial dentures or for making crowns, inlays or bridgework. The material is easily removed from the hands, face, dental instruments or the bowl in which it is mixed. It is not capable of reuse and therefore the patient is assured of completely sanitary operation by the dentist.

The dry powdered material and the liquid may be readily packaged and distributed to the dentist and dental technicians and they are immediately ready for use without employing any special equipment. The various alternative compositions which may be produced in accordance with our invention render it possible to supply dentists and dental technicians with impression compositions which are particularly suited to any special needs or technique without departing from the present invention. In view thereof it should be understood that the particular compositions, proportions and methods of employing products embodying our invention as specifically set forth in the foregoing examples are intended to be illustrative only and are not intended to limit the scope of our invention.

We claim:

1. A composition for use in making dental impression material comprising a mixture containing zinc oxide, at least an equal weight of a copolymer of vinyl chloride-acetate and a minor proportion of dinormal propyl phthalate.

2. A composition for use in making dental impressions comprising the product resulting from a reaction between a powder containing a mixture of zinc oxide and at least an equal amount of vinyl chloride-acetate copolymer containing from 80 to 93% of vinyl chloride and a liquid containing from to parts of dinormal propyl phthalate and from 5 to 10 parts of butyl acetate, said liquid and powder being combined in the proportions of approximately 25 parts of powder to from 18 to 75 parts by weight of liquid.

3. A dental impression composition consisting of a gel-like body comprising approximately 25 parts by weight of a copolymer of vinyl chloride-acetate containing from 80 to 93% of vinyl chloride, and from. 18 to 75 parts by weight of a solvating agent comprising a major portion of di-normal propyl phthalate and a minor portion of butyl acetate, said composition containing a finely divided inert filler in amount not exceeding the weight'of said copolymer.

FRANK J. SOWA. MAX M. SCHWARTZ.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,214,127 Ensminger Sept. 10, 1940 2,310,889 Becker Feb. 9, 1943 2,413,294 Curtis Dec. 31, 1946 2,428,453 Field Oct. 7, 1947 2,447,398 Supinski Aug. 17, 1948 

3. A DENTAL IMPRESSION COMPOSITION CONSISTING OF A GEL-LIKE BODY COMPRISING APPROXIMATELY 25 PARTS BY WEIGHT OF A COPOLYMER OF VINYL CHLORIDE-ACETATE CONTAINING FROM 80 TO 93% OF VINYL CHLORIDE, AND FROM 18 TO 75 PARTS BY WEIGHT OF A SOLVATING AGENT COMPRISING A MAJOR PORTION OF DI-NORMAL PROPYL PHTHALATE AND A MINOR PORTION OF BUTYL ACETATE, SAID COMPOSITION CONTAINING A FINELY DIVIDED INERT FILLER IN AMOUNT NOT EXCEEDING THE WEIGHT OF SAID COPOLYMER. 